The long-term objective of the proposed project is to develop a novel anti-angiogenic therapy for retinopathy of prematurity (ROP), a rare pediatric disease causing life-long disability. Clinical significance: Advances in neonatal care enable survival of many preterm newborns, but these infants are plagued by increased incidence of retinopathy of prematurity, which became a leading cause of childhood blindness worldwide. ROP radically diminishes quality of life of affected individuals and their families. Standards-of-care, laser- or cryotherapy, treat pathological changes, but lead to other retinal damage. The main cause of ROP is overproduction of pro-angiogenic vascular endothelial growth factor (VEGF). Despite promising early outcomes, long-term clinical studies using VEGF antibody bevacizumab in ROP showed recurrent neovascularization leading to retinal detachment, with prolonged lowering of VEGF levels in circulation. Since VEGF is required for normal development of retina and other tissues, there is an acute need for novel ROP drugs that suppress ocular angiogenesis without blocking VEGF. The objective of this proposal is to test the novel anti-angiogenic agent, PMD-336, in a mouse model of ROP, oxygen-induced Ischemic retinopathy (OIR). PMD-336 is a 9 amino acid peptide based on Pigment Epithelium-Derived Factor (PEDF), an endogenous anti-angiogenic glycoprotein that maintains vascular balance in normal tissues, including the eye. PMD-336 is a potent anti-angiogenic agent, acting without VEGF blockade. As a drug candidate, it has several novel and unique features: (1) Drug-like qualities: PMD-336 is the shortest peptide that still retains PEDF?s anti-angiogenic functions; (2) PMD-336 shows no toxicity against retinal cells; (3) It is retinoprotective: Similar to PEDF, PEDF-derived PMD peptides protect retinal pigment epithelium from oxidative stress, and demonstrate anti-fibrotic activity. PMD-336 development as a ROP drug candidate is de-risked by its strong anti-angiogenic activity in another neovascular eye disease model, laser-induced choroidal neovascularization (CNV), without adverse effects. In Aim 1, the effective dose of PMD-336 in mouse OIR will be determined and compared with the antibodies against mouse VEGF164 (AF-493), commonly used as a positive control in OIR. It will be also tested, whether combining PMD-336 with AF-493 could produce additional benefits vs each single agent. The suppression of retinal and vitreal neovascularization will be used as primary, and fibrosis and inflammation as secondary read- outs. In Aim 2, intravitreal PK and safety range of PMD-336 will be assessed in rabbits, with weight, behavior and general pathology as quantifiable safety read-outs. The positive outcome of the proposed feasibility study will justify an investment into further drug development of PMD-336, with the ultimate goal of a novel, potent and safe drug that will become a major therapeutic advance, preventing disability in infants with ROP.